Two- and three-layer resist recording media and their use in forming patterned layers on a substrate having topographical features are well known. Such media are generally comprised of an organic planarizing layer overlying the substrate and a patterning or resist layer overlying the planarizing layer. In a conventional tri-layer system, these layers are separated by an intermediate layer, generally an inorganic oxide or nitride, which functions as a hardmask for dry etching of the planarizing layer.
A significant problem in the use of multilayer resist systems such as described above is the definition of a pattern at a topographical step in the underlying substrate. Frequently, the pattern becomes constricted above the step. This phenomenon, known as "notching" or "necking", occurs with most conventional resist systems. Experience has shown that notching of a pattern feature, which occurs over a step, increases with the height of the step and, to a lesser degree, with the thickness of the layers that must be patterned over the step. It will be appreciated that, as the surface of a semiconductor substrate becomes more complex and the lithographic patterns to be defined shrink to less than one micrometer, there is an increasing need to better define lithographic patterns over steps in substrate topography. Such an improvement is provided in accordance with this invention.